In my experience it does not. However, it is possible that the order matters. Perhaps it honors whatever comes last in the options? It would need testing to be sure.
How do I do that?
According to your output above, subvolid 256 is available at timeshift-btrfs/snapshots/2023-08-12_15-14-06/@.
You could the find command to search that path for files newer than a certain date/time.
If you could list a full command that would be good
I just tested your last theory, edited the fstab and put a wrong subvolid in /etc/fstab and it didn’t work
Even putting the correct subvolid of the timeshift @ subvol in the last doesn’t do that and im still mounting in the correct subvol.
Could it be that timeshift subvols are readonly and they are not booting it up? lol
I would say subvol takes precedence at least in my configuration
Edit : Just for testing purposes I put subvolid of my cache partition in the /@ in my fstab, still same result.